Technical Field
The present disclosure relates to a method for producing bent optical fibers and a connector having the bent optical fibers built-in, and more particularly relates to a method for producing bent optical fibers including removing surface defects resulting from a bending process, and an optical connector with built-in bent optical fibers produced by the producing method.
Background
In recent years, with an increase in the speed of electronic circuits, there is an ongoing development in optical interconnects for performing communications in which light is used for data transmission between devices, circuit boards, or semiconductor chips, since there is a limit on an increase in speed with conventionally used copper wiring and the like.
An optical interconnect may be, for example, a system in which a vertical-cavity surface-emitting laser (VCSEL) is mounted on a circuit board, and transmission of an optical signal is performed by letting an optical signal emitted from the VCSEL enter and propagate through an optical fiber and receiving the optical signal by a photodiode mounted on a circuit board. Since a VCSEL is generally mounted parallel to a circuit board for space-saving and a low-profile circuit board, the emission direction of laser light emitted from the VCSEL is perpendicular to the circuit board. Furthermore, to perform transmission of an optical signal through an optical interconnect, light needs to be propagated parallel to the circuit board. Therefore, there has been proposed a bent optical fiber for vertically bending an optical signal emitted from a VCSEL, and a method for producing the same.
FIG. 12 is a perspective view illustrating a conventional method for producing a bent optical fiber. In this producing method, first, a portion of an optical fiber 110 from which a covering 102 has been removed is placed on a cylindrically shaped cartridge heater 104, and one end of the optical fiber 110 is fixed, and the other end has a weight 109 attached thereto. Accordingly, the portion of the optical fiber 110 in contact with the cartridge heater 104 is bent through an angle of about 90° by the gravity on the weight 109. Thereafter, the optical fiber 110 is annealed at a high temperature to remove a strain generated in the bent portion (Japanese Laid-Open Patent Publication No. S64-49002).
Furthermore, as another conventional method for producing a bent optical fiber, there has been proposed a method of, as shown in FIG. 13, placing a portion 204 of an optical fiber 201 between electrodes 203, and while being brought to a high temperature (equal to or higher than an inflection point, equal to or lower than a softening point) by an arc discharge 202 or the like, bending the optical fiber 201 with a predetermined radius. The bent portion of this optical fiber 201 is bent while it is in a high-temperature state, and after having been bent, it is brought to room temperature. Therefore, a strain caused by the bending is removed from the bent portion (Japanese Laid-Open Patent Publication No. 2005-292718).
On the other hand, as a conventional method for producing an optical fiber, there is a technology in which a ribbon-type optical fiber drawn from a base material is allowed to pass between a pair of guide rollers arranged opposite to each other, and reheating the ribbon-type optical fiber by allowing the ribbon-type optical fiber that has passed through the pair of guide rollers to pass through a continuous reheat furnace. In this technology, a scratch produced on the ribbon-type optical fiber by coming into contact with the pair of guide rollers is melted and removed by applying heat. Thereby a high-strength optical fiber can be obtained (Japanese Laid-Open Patent Publication No. H7-113918).
However, in the above-described technology of Japanese Laid-Open Patent Publication No. S64-49002, a plurality of minute scratches (surface defects) are formed on the surface of the optical fiber that has been bent by being pressed against the cartridge heater. Thus the strength of the optical fiber is significantly reduced, and becomes a cause of breaking of the optical fiber.
Furthermore, in the case of bending an optical fiber using a non-contact heat source, such as arc discharge like the above-described technology of Japanese Laid-Open Patent Publication No. 2005-292718, it is difficult to obtain a desired shape, i.e., a highly accurate bent shape with a desired angle, and the bending angle may widely vary.
Moreover, if the reheating method of Japanese Laid-Open Patent Publications No. H7-113918 is applied to remove scratches made on the bent portion in Patent Document 1, the entire bent optical fiber needs to be passed through the continuous reheat furnace, and there may be a case where optical propagation characteristics of the bent optical fiber after the removal of scratches cannot be maintained.
The present disclosure is related to providing a method for producing a bent optical fiber, which is capable of obtaining a highly accurate bent shape and enhancing the strength and further has good optical propagation characteristics after the removal of a defect, and a connector having said bent optical fibers built-in.